<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <button id="btn1">按钮1</button>
    <button id="btn2">按钮2</button>
    <button id="btn3" onclick="handleCli()">按钮3</button>
  </body>
  <script type="text/javascript">
    const btn1 = document.getElementById("btn1");
    const btn2 = document.getElementById("btn2");
    btn1.addEventListener("click", () => {
      alert("按钮1被点击了");
    });
    btn2.onclick = () => {
      alert("按钮二被点击了");
    };
    function handleCli() {
      alert("按钮三被点击了");
    }
  </script>
</html>
